Get something small, maybe something like a Lenovo ThinkCentre mini. Put Proxmox on it and install HAOS as a VM. Then when you want to add software, add them as LXC containers on the Proxmox host. Like Z-wave, MQTT, ESPHome, zigbee, etc. I really like having things in separate containers so that way I can work on things separately. If I need to restart the HAOS VM, it's a lot faster because my entire Z-wave network doesn't have to restart.
Avoid adding things that require cloud access. I have to have a damned good use case before I add anything that requires Internet access.
Oh and I like this place: https://cloudfree.shop/